One of my favorite bits is from By Any Other Name, where Scotty is trying to get an alien drunk. After they go through every other bottle he has, Scotty brings out the last, precious bottle. The now barely-on-his-feet alien asks what it is. Scotty looks at it, swaying a bit, and finally says "It's green!" The alien takes a swig and then falls down drunk. Scotty retrieves the item from the alien's belt that he was after, gets as far as the door, and then collapses himself. (In Star Trek: The Next Generation, Data uses the same line in Relics when Scotty is in Ten Forward and wants a drink.)

"Just before they went into warp, I beamed the whole kit and kaboodle into their engine room, where they'll be no tribble at all." -- Scotty, explaining how he got rid of the tribbles (The Trouble With Tribbles)

Here's a trivia question: What was the name of the sequel to The Trouble With Tribbles?